This application relates to hatch covers for cargo carrying vessels such as the hopper of a railway covered hopper car and latch structures for such hatch covers, and is a continuation in part of U.S. application entitled "Hatch Cover Assembly" U.S. Ser. No. 07/353,543, Filed 05/18/89.
Locking arrangements for lockingly sealing a hatch cover to a hatch opening defined by a combing of a vessel such as a railway covered hopper car are old and well known. The contents laded in a given vessel may have properties such that excessive pressures build up inside the vessel when the hatch is sealed. When the locking arrangement of the hatch cover is released, the excess pressure may swing the hatch cover open with considerable force potentially damaging the apparatus. To prevent this, the locking arrangement may be designed to retain the hatch cover in an intermediate "blow-off position" where the hatch cover is free to move and vent excessive pressure, but is restrained against larger movements potentially causing harm.
A number of patents have issued relating to hatch covers among which are the following:
U.S. Pat. No. 4,690,070 issued to Roy W. Miller on Sept. 1, 1987, describing a HATCH COVER STRUCTURE to include a clip securing the hatch cover to a hold down bar.
U.S. Pat. No. 4,655,365 issued to Roy W. Miller on Apr. 7, 1987, describing a HATCH COVER LOCK to include a stop member which supports the hatch cover when the hatch cover is pivoted open.
U.S. Pat. No. 4,622,902 issued to Roy W. Miller on Nov. 18, 1986, describing a HATCH COVER AND LOCKING STRUCTURE to achieve adjustable sealing pressure.
U.S. Pat. No. 4,570,816 issued to Ferris et al. on Feb. 18, 1986, describing a HATCH COVER AND LOCKING STRUCTURE to achieve adjustable sealing pressure.
U.S. Pat. No. 4,388,873 issued to Carleton et al. on June 21, 1983, describing a RAILROAD VEHICLE to include a catch which prevents the hatch from being blown open.
U.S. Pat. No. 4,248,160 issued to Carney, Jr. on Feb. 3, 1981, describing a RAILWAY HATCH COVER COVER AND STRAP LATCHING ASSEMBLY which includes a over center latch handle with a longitudinal stiffening member.
U.S. Pat. No. 3,228,353 issued to Carney, Jr. on Aug. 5, 1963, describing a HATCH COVER STRUCTURE FOR RAILWAY CARS.
U.S. Pat. No. 1,613,830 issued to Hull on Jan. 11, 1927, describing a VENTILATING DOOR FOR THE HATCHWAYS OF REFRIGERATING CARS.
Despite the foregoing, improvements in the manner of maintaining sealing pressure, insuring ease of rotation of the hatch and preventing damage to the latch handle and hatch were desirable.